The Food and Drug Administration approved Kynamro to treat homozygous familial hypercholesterolemia, or HoFH. This is a rare form of inherited high cholesterol associated with a greatly increased risk of cardiovascular disease.

Kynamro lowers the level of LDL-C, the so-called “bad” cholesterol, associated with heart disease. Generically called mipomersen, Kynamro will be sold by Genzyme, a unit of French drug giant Sanofi.

Kynamro, the first Isis drug approved in many years, uses the Carlsbad company’s gene-blocking antisense technology. Isis has more than a dozen other antisense drugs in clinical trials for a number of diseases. While the limited approval represents a smaller market than Isis and Genzyme envisioned when they announced their partnership in 2008, approval represents a commercial validation that antisense, which works in the lab, can also produce drugs that can be sold.

“We think it’s a seminal day for those with homozygous FH, for Kynamro, for our pipeline, for the technology we’ve invented, and for Isis,” said Stanley Crooke, Isis’ chief executive officer.

Isis will get a $25 million milestone payment from Genzyme for the approval, Crooke said.

Kynamro may generate $403 million in peak sales by 2020, said Philippe Lanone, an analyst with Natixis Securities in Paris. Isis will get 30 percent to 50 percent of Kynamro profits based on drug sales, according to a 2008 agreement with Paris-based Sanofi. The deal brought Isis $325 million upfront.

Kynamro faces competition from Juxtapid, another cholesterol medication, which the FDA approved in December. Juxtapid was endorsed Oct. 17 by an FDA advisory committee on a 13-2 vote. The next day, the same committee recommended approval of Kynamro, on a 9-6 vote.

Kynamro’s safety and effectiveness were evaluated in a clinical trial of 51 patients with the genetic disease. On average, levels of LDL-C fell by about 25 percent during the first 26 weeks in those receiving Kynamro, the FDA said in its approval statement.

“Kynamro, an injection given once a week, works with other lipid-lowering medications and diet to impair the creation of the lipid particles that ultimately give rise to LDL-C,” the FDA’s Eric Colman said in a news release. Coleman is deputy director of the Division of Metabolism and Endocrinology Products at the FDA’s Center for Drug Evaluation and Research.

The FDA approval comes with what’s called a Risk Evaluation and Mitigation Strategy to reduce the chance of bad reactions. Kynamro will also carry a boxed warning on the risk of liver damage, because it is associated with liver enzyme abnormalities and accumulation of fat in the liver. The FDA says this accumulation could lead to progressive liver disease with chronic use.

The most-common unwanted side effects in the clinical trial included injection site reactions, flu-like symptoms, nausea, headache and elevations in liver enzymes called serum transaminases, the FDA said.